U.S. Pat. Nos. 4,483,125 and 4,571,972 disclose packaging apparatus, consisting in continuously drawing band-like rolled film from its end installed in a film storage source, putting said film on articles by rounding said film to be tubular around said articles while the latter are transported substantially parallelly to said film, cutting the tubular film between adjacent articles, and folding the opposite ends of the cut film onto its bottom surface. When the film is to be folded, the opposite ends of the film are pulled at right angles to the article by air currents and the front film end as viewed in the transport direction of the article held in contact with a fixed wall plate is folded onto the bottom of the article by the force with which the article is being transported. The rear film end as viewed in the transport direction of the article is folded onto the bottom surface of the article by moving a bar-like roller along the bottom surface of the article at a higher speed than that at which the article is being transported, so as to arrest the film end by said bar-like roller. Such film for use for packaging is thin and stretchable and has a property which resembles self-adhesion; thus, the film end folded along the bottom surface of the article adheres to the film covering the bottom surface of the article and is thereby held in position.
However, since the bar-like roller moves faster than the article, it sometimes occurs that when said roller passes below the front ends of the film after folding the rear end of the film, the roller comes in contact with the front end, stripping the front end of the film again which has already been folded onto the lower surface of the article. Further, in practice, a plurality of such bar-like rollers are disposed in an endless manner and in parallel to each other and travel intermittently in such a manner that they stop each time after they have made a round of an endless path so as to fold the rear end of the film onto the bottom surface of the article. However, since the article is being transported even during this stopped state of the bar-like rollers, it sometimes happens that the rear end of the film once folded is caught by a bar-like roller which is stopping after travel, whereby the rear end of the film is stripped again. Thus, this type of apparatus has a drawback that there are always defectively sealed articles amounting to about 2-3%.
With the above in mind, the object of the present invention is to prevent the front and rear ends of a film from being stripped from the lower surface of an article to be packaged by bar-like rollers for folding the rear end of the film onto the bottom surface of the article by using means adapted to avoid contact between the bar-like roller and the front and rear ends of the film already folded along the lower surface of the article.
To achieve this object, the packaging apparatus of the invention comprises:
means for transporting a plurality of articles to be packaged which are covered with a tubular film so that they are spaced from each other,
means for cutting the tubular film between adjacent articles to form a film end which is disposed forwardly in the transport direction and a film end which is disposed rearwardly in the transport direction for each article,
means for pulling both film ends respectively by air currents toward the bottom of the article, fixed wall means adapted to engage the front film end to fold said front film end onto the bottom of the article by the force with which the article is transported,
bar-like roller means adapted to move along the bottom surface of the article at a higher speed than the transport speed of the articles, thereby catching the rear film end to fold the latter onto the bottom side of the article, and
means extending along the path of travel of said bar-like roller means and designed to blow air to urge the front and rear film ends against the bottom surface of the article.
With such arrangement, the pressure of the air blown out of the air blow means urges the front and rear film ends against the bottom surface of the article; thus, the bar-like roller is prevented from contacting the urged film ends; the front and rear film ends are prevented from being stripped from the bottom surface of the article. As result, the rate of occurrence of defectively sealed articles can be reduced.